Indane synthesis



March 19, 1963 TOLUENE, ETHYLENE CUMENE HYDROPEROXIDE E. A. HUNTER ETAL 3,082,267

INDANE SYNTHESIS Filed March 1, 1960 I LO I I0 m LU 5 o LU N I.- z m o n: w n.

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IO 0 o N N 0 Ln Edward Allen Hunter Clyde Lee Aldrldge Inventors chain. 20 to 30 wt. percent may be obtained, which, of course,

United States Patent 3,082,267 INDANE SYNTHESIS Edward Allen Hunter and Clyde Lee Aldridge, Baton Rouge, La., assiguors to Esso Research and Engineering Company, a corporation of Delaware Filed Mar. 1, 1960, Ser. No. 12,049 10 Claims. (Cl. 260-668) The present invention relates to an improved process for the production of indanes. More particularly, this invention relates to a process wherein an alkyl benzene compound is reacted with ethylene in the presence of free radicals under carefully chosen reaction conditions. Thus, high yields of indanes are obtained along with the production of alkyl benzene compounds having on the average less than 7 carbon atoms in the alkyl group. Most particularly, this invention relates to reacting an alkyl aromatic with 2 to 20 mol percent of ethylene at temperatures of 200-350 C., pressures of 400-800 p.s.i.g., in the presence of a reaction initiator. This reactioninitiator may be a compound which decomposes thermally to yield'free radicals, e.g. a peroxide or the free radicals may be generated by such expedients as exposing the reaction mixture to ionizing radiation.

According to the present invention it has now been discovered that extremely valuable indanes may be produced from inexpensive alkyl benzene compounds (such as toluene) and ethylene. The reaction of these compounds to produce long chain alkyl benzene compounds is known in the art. Surprisingly it has now been discovered over said known reactions that by drastically limiting the amount of ethylene supplied and by control of the pressures and temperatures utilized it is possible to obtain cyclization rather than a growth of thev alkyl Thus, s'electivities per pass to indane of about can be increased by recycling the alkyl benzene product also obtained in the process. It should be noted that the alkyl benzene side product contains on the average only 3 to 6 carbon atoms in the alkyl chain as compared to the average of 7 to 20 carbon atoms in the alkyl chain obtained in the prior art processes.

According to the present invention the indanes or substituted indanes may bep'repared by reacting ethylene with alkyl benzene compounds having at least one alkyl group containing not more than 10 carbon atoms, said alkyl group having at least one hydrogen atom attached to a saturated carbon atom alpha to the benzene ring.

- The compound preferably has no additional substitutions,

additional alkyl substituents being particularly undesirable because this multiplicity of reaction sites permits the possibility of undesirable multiple reactions on a single molecule. Specific compounds which may preferably be used are toluene and isopropylbenze-ne (i.e. cumene),

( 1 Radical R- @011. an Gem O-Om- CH2=CH2 @omomon,

3,082,267 Patented Mar. 19, 1963 ice O-om'omom- II- H-reinitiates reaction wherein R and R are hydrogen or an alkyl group and n is an integer which under the preferred conditions of operation presently disclosed will be 1 to 3 for most of the product. It should be noted that both R and R in the above formula are present in the alkyl benzene starting material reacted with ethylene.

The conditions for carrying out the present invention are as follows: Temperatures of 200 to 350 F., preferably 250 to 300 F.; pressures of 400 to 800 p.s.i.g., preferably 500 to 700 p.s.i.g.; mol ratio of ethylene to alkylated benzene in the range of 2 to 20 mol percent, preferably 5 to 15 mol percent ethylene. Reaction times may be from 0.25 to 10 hours, preferably 2 to 5 hours.

' Where the reaction initiator is an unstable material quanof 0.5 to 1 weight percent of catalyst is generally pre-' ferred. Increasing amounts of catalyst tend generally to decrease the amount of residue formed, i.e. high boiling 1 material.

The alkyl benzene may also be advantageously diluted with about 1 to 4 moles of an inert diluent, preferably a hydrocarbon diluent (e.g. benzene) per mole of alkyl benzene, in order to increase the ratio of indanes to alkyl benzenes obtained in the products. Since these diluents must be inert in the reaction carried out most materials such as paraffins and cycloparafiins are unsuitable. Therefore, as mentioned above, preferably the diluent is benzene, which is inert in the reaction, cheap, and easily separated from the products by distillation.

Systems which may be used to initiate the reaction, i.e. liberate free radicals, may be either unstable compounds which decompose under the reaction conditions such as peroxide materials, persulfates, etc. or physical means for producing free radicals such as ionizing radiation, e.g. obtained from a Van de Graaif accelerator or a nuclear energy source, such as a cobalt 60 source.

Examples of the unstable compounds which may be utilized are hydrogen peroxide; hydroperoxides, having no elements other than carbon, hydrogen and oxygen-in the molecule, e.g. cumene hydroperoxide, tetralin hydroperoxide, toluene hydroperoxide, tertiary butyl hydroperoxide, the crude hydroperoxides obtained upon passing air through hydrocarbons such as petroleum in liquid phase and alkyl peroxides, e.g. di-tertiary butyl peroxide. Other peroxy catalysts which are stable, or only slowly decompose, below about- C. can also be used, e.g. benzoyl Peroxide, di-tertiary butyl peroxide, bis-Z-phenylpropyl-peroxide-Z, alkali metal salts of persulfuric acid, etc.

With respect to available physical means for initiating the reaction, such sources as cobalt 60 sources, Van de Graafr" accelerators, and atomic piles may be used. The

advantages for these sources, of course, is that they are more economical.

In the case Where reaction is initiated with a peroxide or hydroperoxide, the initiator is preferably added as a series of increments at intervals throughout the course of the reaction.

The present invention will be more clearly understood from a consideration of the following examples.

Example 1 69 mol percent toluene and 31 mol percent ethylene were mixed in an autoclave at 250 C. and 1000 p.s.i.g. To this mixture was added 1.46 g. of cumene hydroperoxide per liter of toluene in 10 equal increments at 15 minute intervals. Reaction conditions were held for a total of hours.

Mass spectrographic analysis of the product boiling above toluene gave a weighted average of: 9 wt. percent indanes 91 wt. percent alkyl benzenes Further it was found that the yield of this product was 26 weights per weight of initiator used.

Example 2 A reaction was carried out similarly to Example 1 under the following conditions.

1500 p.s.i.g.

1.46 g. cumene hydroperoxide per liter toluene 87.5 mol percent toluene 12.5 mol percent ethylene, reaction time 1 hour.

The product boiling above toluene was analyzed by mass spectrometer and was found to contain 16 wt. percent indane and 84 wt. percent alkyl benzene. The yield was weights of material boiling above toluene per weight initiator.

The improvement in yields of indanes obtained by.

utilizing less than 20 mol percent of ethylene may be seen from the accompanying drawing depicting a plot of weight percent indane yield vs. mole percent of ethylene based on toluene in the system. Thus it can be seen that extremely low ethylene concentrations result in large increases in the yields of indanes obtained.

Additionally for comparison purposes a run was made wherein no ethylene was added to the reactor. Thus a one liter stirred autoclave was charged with 250 mls. of n-propylbenzene. The autoclave was heated to 250 C. and 1.46 g. cumene hydroperoxide diluted to 20 cc. with n-propylbenzene was added as the initiator solution. This solution was added in ten 2 cc. portions at minute intervals holding the reactor temperature constant at 250 C. Following completion of the reaction the bomb was cooled and held overnight. The product was then transferred to a still pot and most of the n-propylbenzene distilled 01f, leaving 8.8 grams of bottoms in the pot. The bottoms were filtered and analyzed by mass spectrometer and gas chromatographic equipment. Both analyses showed the bottoms to be predominantly C aromatics with no more than unmeasurable traces of indane structures present.

From this data it can be seen that preparation of indanes occurs by a true addition or telomerization reaction rather than by simple cyclization.

Example 3 As Example 2 above but cumene was used in place of toluene. Product contained about 1020 wt. percent methyl substituted indanes.

Example 4 Utilizing a procedure similar to that used in Example 1 toluene and ethylene are reacted as follows:

300 C. 500 p.s.i.g.

1.46 g. cumene hydroperoxide per liter toluene mol percent toluene 10 mol percent ethylene 3 moles benzene diluent per mole toluene Over 30 wt. percent indanes will be obtained Remainder alkyl benzenes It is to be understood that this invention is not limited to the specific examples, which have been offered merely as illustrations, and that modifications may be made without departing from the spirit of this invention.

What is claimed is:

1. An improved process for preparing indanes which comprises reacting an alkyl benzene having an alkyl group containing not more than 10 carbon atoms, said alkyl group having at least one hydrogen atom attached to a saturated carbon atom alpha to the benzene ring, with 2-20 mol percent of ethylene at temperatures of 200 to 350 C., pressures of 400 to 800 p.s.i.g., and in the presence of a free radical initiator, and recovering indanes from the reaction mixture.

2. The process of claim 1 in which the alkyl benzene is diluted with about 1 to 4 moles of benzene per mol of alkyl benzene.

3. An improved process for preparing indanes which comprises reacting in the presence of a peroxy catalyst having no elements other than carbon, hydrogen and oxygen in the molecule and which is substantially stable below C., an alkyl benzene having an alkyl group containing not more than 10 carbon atoms, said alkyl group having at least one hydrogen atom attached to a saturated carbon atom alpha to the benzene ring and 2-20 mol percent of ethylene at temperatures of 200 to 350 C., pressures of 400 to 800 p.s.i.g., and recovering indanes from the reaction mixture.

4. The process of claim 3 in which the alkyl benzene is diluted with about 1 to 4 moles of benzene per mol of alkyl benzene.

5. The process of claim 3 in which the amount of peroxy catalyst is about 0.1 to 5 wt. percent based on the alkyl benzene reactant.

6. The process of claim 3 wherein the alkyl benzene reactant is toluene and the catalyst is cumene hydroperoxide.

7. The process of claim 3 in which the alkyl benzene reactant is cumene and the catalyst is cumene hydroperoxide.

8. The process of claim 3 in which alkyl benzene byproducts from the reaction are recycled to the process.

9. An improved process for preparing indanes which comprises reacting, in the presence of a peroxy catalyst having no elements other than carbon, hydrogen and oxygen, an alkyl benzene having an alkyl group containing not more than 10 carbon atoms, said alkyl group having at least one hydrogen atom attached to a saturated carbon atom alpha to the benzene ring, 1 to 4 moles of benzene per mole of alkyl benzene, and 5-15 mol percent of ethylene based on the alkyl benzene at temperatures of 250 to 300 C. and pressures of 500 to 700 p.s.i.g., the amount of said catalyst being 0.1 to 5 wt. percent based on the alkyl benzene reactant; and recovering indanes from the reaction mixture.

10. An improved process for preparing indan which comprises reacting toluene diluted with 1 to 4 moles of benzene per mol of toluene with 5-15 mol percent of ethylene i nthe presence of 0.1 to 5 wt. percent of cumene hydroperoxide catalyst based on toluene, at temperatures of 250 to 300 C. and pressures of 500 to 700 p.s.i.g. and recovering indan from the reaction mixture. 4

Erchak, Jr Nov. 24, 1953 Pines et al May 29, 1956 1 l l I 

1. AN IMPROVED PROCESS FOR PREPARING INDANES WHICH COMPRISES REACTING AN ALKYL BENZENE HAVING AN ALKYL GROUP CONTAINING NOT MORE THAN 10 CARBON ATOMS, SAID ALKYL GROUP HAVING AT LEAST ONE HYDROGEN ATOM ATTACHED TO A SATURATED CARBON ATOM ALPHA TO THE BENZENE RING, WITH 2-20 MOL PERCENT OF ETHYLENE AT TEMPERATURES OF 200 TO 350*C., PRESSURES OF 400 TO 800 P.S.I.G., AND IN THE PRESENCE OF A FREE RADICAL INITIATOR, AND RECOVERING INDANES FROM THE REACTION MIXTURE. 